The present disclosure relates to optical devices to which a corrosion-inhibiting monolayer has been applied for the purpose of protecting the silver surface(s) of the device. Also disclosed are methods for producing such devices.
Optical coatings are layers of material deposited on optical components, such as lenses or mirrors, which alter the way in which the optical component reflects and transmits light. Thus optical coatings are used in a wide range of optical applications, such as astronomy, still and video cameras and other imaging devices, televisions, computer monitors, cellular telephone screens and other display devices, optical sensors such as motion sensors, gesture sensors, and the like. Depending on the application, the coatings can vary in thickness and design.
Silver has shown to have superior reflective properties in the visible spectrum, particularly when compared to gold. However, silver is generally avoided in high precision imaging applications due to its inferior environmental resistance and its softness. For example, sulfidation of silver by sulfur-containing gases trapped in humid air has been well-documented by the scientific community.
Dielectric layers are sometimes applied over top of metal films, either functioning as protective layers that increase abrasion resistance, or to enhance the reflectivity of the metal films. Metal and dielectric combinations are also used to make advanced coatings tailored in sensitivity to wavelength, angle and polarization. The overall reflectivity and transmissive capability of the optical device may be tailored based on composition, thickness and number of layers. However, defect sites in these protective layers, such as pinholes, can serve as entry points for sulfidative compounds that can attack silver. It would be desirable to develop coatings that reduce sulfidation and other adverse effects resulting from imperfect and/or perforated dielectric layers, and to provide methods for applying such coatings to optical devices.